Polystyrene Particles Reveal Pore Substructure As They Translocate

Matthew Pevarnik†, Ken Healy†‡*, Maria EugeniaToimil-Molares§, Alan Morrison‡, Sonia E. Létant, and Zuzanna S. Siwy†*

^† Department of Physics and Astronomy, University of California, Irvine, Irvine, California 92697, United States

^‡ Department of Electrical and Electronic Engineering,University College Cork, Cork, Ireland

^§ Department of Materials Science, GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany

 Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, California 94550, United States

In this article, we report resistive-pulse sensing experiments with cylindrical track-etched PET pores, which reveal that the diameters of these pores fluctuate along their length. The resistive pulses generated by polymer spheres passing through these pores have a repeatable pattern of large variations corresponding to these diameter changes. We show that this pattern of variations enables the unambiguous resolution of multiple particles simultaneously in the pore, that it can detect transient sticking of particles within the pore, and that it can confirm whether any individual particle completely translocates the pore. We demonstrate that nonionic surfactant has a significant impact on particle velocity, with the velocity decreasing by an order of magnitude for a similar increase in surfactant concentration. We also show that these pores can differentiate by particle size and charge, and we explore the influence of electrophoresis, electroosmosis, and pore size on particle motion. These results have practical importance for increasing the speed of resistive-pulse sensing, optimizing the detection of specific analytes, and identifying particle shapes.